Production of carbon monoxide and hydrogen



Nov. 17, 1970 a. BARON ETA!- '1 3,540,357

PRODUCTION OF CARBON MONOXIDE AND-HYDROGEN Filed May 10. 1967 2Shee'ts-Sheet 1 Inventors:

Gerhard ZBordn, Ernst K p, Heriber @Prhbaa 'franz Biegwand 7% o/f Koh/enBy: W,

Ffttorneys Nov. 17, 1970 Filed May 10. 1967 Fig. 2

s. BARON ET AL 3,540,867

PRODUCTION OF CARBON MONOXIDE AND HYDROGEN 2 Sheets-Sheet 2 awfitter/ways United States Patent 3,540,867 PRODUCTION OF CARBON MONOXIDEAND HYDROGEN Gerhard Baron and Ernst Kapp, Frankfurt am Main, HeribertDernbach, Frankfurt, Franz Bieger, Dorsten, and Rudolf Kohlen,Pfafrenwiesbach, Germany, assignors to MetallgesellschaftAktiengesellschaft, Frankfurt am Main, and Ruhrgas Aktiengesellschaft,Essen, Germany Filed May 10, 1967, Ser. No. 637,603 Claims priority,application Germany, May 20, 1966, M 69,561 Int. Cl. Cj 3/02; C10k 1/02,N04 US. Cl. 48197 10 Claims ABSTRACT OF THE DISCLOSURE Manufacture ofgases rich in carbon monoxide and/or hydrogen from solid carbonaceousfuels by distillation or by gasification with steam and oxygen, coolingthe hot raw gas from said distillation or gasification to a temperatureabove about 180 C. to remove dust and condensible material, heating saidgas with steam enrichment, adding oxygen thereto and cleaving saidgas-steamoxygen mixture at a temperature above about 700 C. on acleaving catalyst; cooling the gas from said cleavage with or withoutconversion of the carbon monoxide contained therein with steam in theshift reaction and removing CO H 8 and NH from said cooled gas.

This invention relates to the production of gases comprising carbonmonoxide and hydrogen from nongaseous reactants. It more particularlyrefers to improvements in such production whereby undesirable byproductsare reduced or eliminated.

Gases comprising carbon monoxide and hydrogen have known utility asheating gases, synthesis gases and reducing gases. They are extensivelyused in chemical and metallurgical processes. These gases areexemplified by city gas and illuminating gas.

In general, gases of the type described are produced by the coking orgasification of solid carbonaceous materials such as coal. In the cokingof coals, the coke forms the largest percentage of the product. Thedistillation products are tar and tar oil, ammonia liquor and gas. Inthe gasification of coals with oxygen and/or air and steam, the mainproduct is a gas consisting mainly of carbon monoxide and hydrogen. Tarand water are byproducts. The ash is Waste. In comparison with coking orlow-temperature carbonization, a relatively large volume of gas of lowheat value is produced, which contains in greatly diluted form the tarformed in the gasification process. This dilute tar tends to complicatethe purification by scrubbing of the gas. If the gasification isperformed under pressure, the gas also contains a percentage of methane,which methane quantity increases with the pressure.

Tar-free gases can be produced by the gasification of coke. These gasesneed only to be freed of gaseous impurities. This, however, does noteliminate the problem of winning and utilizing the byproducts, butmerely shifts it back to the coking stage.

Whereas liquid and gaseous energy sources, such as petroleum and fuelgas, can be pumped simply and inexpensively through pipelines and can bedistributed to consumers in compound networks, coal still has to betransported to the customer on barges and trucks. In order to put solidfuels on a footing comparable to that of liquid and gaseous fuels, thewinning and utilization of byproducts, especially of tar and ammonialiquor, which today are often negative cost factors, must be greatlyreduced or rendered entirely unnecessary. It is furthermore necessary tocontrol gas manufacture so that the gas that is produced need only bescrubbed to remove a few simple components of the gas, such as H S, COand NH3.

It is in the prior art to increase the heating value of gas produced bypressure gasification by the thermal decomposition of the tar substancescontained in the raw gas. For this purpose, a partial stream is drawnfrom the raw gas after it has passed the scrubber that is directlyconnected to the pressure gasifier. This stream is burned partially bythe addition of oxygen and/ or air, and therefore heats the raw gas. Inthis partial current, hydrocarbons which have condensed out of the mainstream may be injected and decomposed into low gaseous hydrocarbons, seefor example German Pat. 969,851.

It is also in the prior art to transform the carbon monoxide containedin the pressure gasification gas to carbon dioxide and hydrogen byconverting it with water vapor. The excess Water vapor from thegasification, which is contained in the raw gas, may be substantiallyincluded in the reaction. The raw gas is cooled in the scrubber directlyconnected to the pressure gasifier by sprinkling it with the condensatethat is separated from it in the subsequent cooling, this being doneonly to such an extent that high-boiling tar and pitch fractionsprecipitate and take along with them the dust contained in the raw gas.The raw gas containing water vapor and tar oils has then been heated toabout 350 to 400 C. and passed over a sulfur-proof conversion catalystwhich simultaneously has an hydrogenating action. In addition to theconversion of the carbon monoxide, this catalyst induces anhydrogenation of unsaturated hydrocarbons and organic compoundscontaining sulfur, oxygen or nitrogen, with the resultant formation ofhydrogen sulfide, water and ammonia. Liquid hydrocarbons refined byhydrogenation are separated from the converted gas along with water inthe cooling process. After that, carbon dioxide and hydrogen sulfide arewashed out of the gas, see for example German Pat. 1,094,395.

It has been proposed to perform, before or instead of carbon monoxideconversion, a catalytic cleavage of the vaporous hydrocarbons containedin the gas along with hydrocarbons, such as light gasoline, additionallyfed in from the outside. If desired, this cleavage can be accomplishedwith steam at 450 to 650 C. in the presence of a sulfur-resistantcatalyst, so as to form low gaseous hydrocarbons, thus increasing theheating value of the product.

In all these processes which set out from pressure gasification, it iscustomary to feed the heavy tars separated in the scrubber back to thegasifier for further decomposition. In the carbonization processes, too,the return of high-boiling tar fractions to the coking process is alsoknown, e.g., in the briqnetting of fine coals for subsequentlow-temperature carbonization, the briquette binding substance beingobtained from the low-temperature carbonization tar, or in the return ofheavy tar oil to the roof channel of horizontal chamber furnaces for theimprovement of the output of benzol.

It is also in the prior art to gasify fine coals and/or heavy oilsWithout substantial formation of byproducts. Nevertheless, very hightemperatures of 1200 to 1500 C. must be used, and high specificquantities of oxygen must be put in. In this coal gasification process,the ash usually cannot be completely burned out, while in thegasification of heavy oil alone or together with fine coal, the oftenunavoidable formation of poorly reactive carbon black complicates theconduction of the process and the purification of the gas.

It is an object of this invention to provide a novel, improved processfor the production of gases comprising carbon monoxide and hydrogen.

It is another object of this invention to provide a process for theproduction of carbon monoxide and hydrogen containing gases whichsignificantly reduces the byproduct formation from that usuallyassociated with such processes.

Other and additional objects of this invention will become apparent froma consideration of this entire specification, including the claimsappended hereto.

The process according to the invention for the manufacture ofcombustible gases from solid fuels is directed at the problem ofproducing, in the coking or gasification of coal, a gas consistingpredominantly of carbon monoxide and hydrogen, and of limiting thedevelopment of byproducts and waste to water, hydrogen sulfide andcarbon oxy-sulfide, and to carbon dioxide.

If water vapor is going to be used to transform the carbon monoxidecontained in the produced gas into hydrogen and carbon dioxide in orderto manufacture a gas that is very rich in hydrogen, for ammoniasynthesis, for example, it is generally desirable to keep the methanecontent of the raw gas as low as possible. The same applies to a gasthat is to be used for the synthesis of methanol, if in it the CO'zHratio is adjusted by feeding CO back into the gasification rather thanby partial conversion of carbon monoxide.

If the process according to the invention, the volatilized tarsubstances formed in the coking or gasification of the coal are left inthe gas in vapor form insofar as possible, and catalytically decomposedto carbon monoxide, hydrogen and carbon dioxide. Dust and high-boilingtar components which condense out of the raw gas in the course of theprocess are fed back into the gasification. Tar components that aresoluble in the ammonia liquor, consisting mostly of phenols, tar acids,fatty acids and bases, are fed back into the process by injectionvaporization when the raw gas is enriched with Water vapor, forcatalytic cleavage.

The treatment of tar-containing gases according to the invention isapplicable to the raw gases from the coking of coal, i.e., to raw cokinggas or low-temperature carbonization gas, and to the raw gas from coalgasification at normal or elevated pressure with oxygen and water vapor.The technical oxygen can be replaced wholly or partially by air,depending on the nitrogen content permitted in the product gas.

The process of the invention is characterized in that the tar-containinggas coming from the coking or gasification is cooled directly orindirectly to temperatures above about 180 C. and freed of dust andcondensing substances. It is then enriched with water vapor and heatedto about 400 to 550 C. and, after the addition of oxygen, it isdissociated at temperatures above about 700 C. on a cleavage catalyst onhigh-temperature-resistant supporting material. Carbon dioxide, sulfurcompounds and ammonia are suitably washed out of the product gas in aconventional manner from the cleavage gas that is cooled by heatexchange with the raw gas being dissociated.

If desired, carbon dioxide can be added to the raW gas beingdissociated, in addition to the oxygen. Volatile hydrocarbons can alsobe added to the hot, raw gas when it is being cooled for the separationof dust and heavy tar and/or when it is being heated up prior to thecatalytic dissociation.

In the process of the invention, the hot, raw gas, still containing tar,is first cooled and, if desired, washed with water in order to separateany pitch and coal dust therefrom, to bring to condensation thehigh-boiling tar components, and, if desired, to increase the watervapor content of the gas. The water that is put in at this point issuitably that which is removed from the condensate produced in the latercooling of the product gas. This water can be supplemented or partiallyreplaced by outside additional volatile hydrocarbons.

The gas freed of dust and heavy tar is hen heated to about 400 to 550C., suitably with the hot product gas by indirect heat exchange. Thewater vapor content is further increased by the injection vaporizationof ammonia liquor which is produced in the process. By this measure thewater-soluble tar fractions and also the ammonia are fed back into theprocess. At this point, too, volatile hydrocarbons of other origin canadditionally be introduced into the gas, if desired.

The gas, which is now rich in hydrocarbon vapors and water Vapor, ismixed with a vaporous source of oxygen, e.g., oxygen, air, etc., andmade to react on a hightemperature-resistant cleavage catalyst at about700 to 1100 C., preferably at about 850 to 1000 C., whereupon a gasdevelops which contains almost exclusively carbon monoxide and hydrogen,as well as some smaller quantities of water vapor and carbon dioxide.The methane content of this gas is low and can be reduced further,almost to the vanishing point, by the proper adjustment of the reactiontemperature in the catalytic reaction. Under mild catalytic reactiontemperature conditions, corresponding to a gas outlet temperature belowabout 850 C., small amounts of aromatics, such as benzene, may occur inthe gas. In that case, too, the ammonia contained in the gas does notbecome fully oxidized and accordingly appears in the aqueous condensatein the final cooling. The ammonia can be driven out of this condensatewith low pressure steam and concentrated. If this concentrate is fedback into the raw gas before cleavage, the ammonia formed in the cokingor gasification of coal is transformed to nitrogen. The only impuritiesto be removed from this gas are hydrogen sulfide, carbon oxysulfide andcarbon dioxide. The only liquid end product is water, which issufiiciently uncontaminated to be pumped directly into a sewer main.

If it is desired that a gas particularly rich in carbon monoxide is tobe produced, a portion of the carbon dioxide washed out of the productgas can be fed back into the gas stream ahead of the catalytic cleavage.If the product gas is to be rich in hydrogen, the catalytic cleavage canbe followed by a conventional system for the conversion of carbonmonoxide with water vapor in the presence of sulfur-resistant catalysts.

For the separation of dust, pitch and heavy tar in the first step of theprocess, different procedures may 'be provided for hot gas producedwithout pressure and for hot gas produced under elevated pressure.

Whenever the hot raw gas is available under elevated pressure of, forexample, 15 to 30 atmospheres gauge, it is preferably washed in thefirst stage with an excess of recirculated water, which washing cools itto about to 200 C. At this temperature the heavy components, especiallythe pitch, condense out and separate from the wash water. They aretapped out of the washer circuit with an amount of water which isapproximately between 0.05 and 0.3 kg./m. (STP) of raw gas, and isseparated from the water by decantation. This dust and tar fraction isfed back into the gasification process. The Water is transferred backinto the washer circuit or sprayed into the heated gas through nozzlesin the second stage.

If the hot gas is produced at about atmospheric pressure, as for examplein high-temperature coking, it should be first cooled to about 350 to400 C., for example by the injection of water. This cooling is bestperformed in a radiation boiler with smooth heat exchange surfaces. Bythis cooling operation, dust, pitch and heavy tar fractions areseparated from the gas. Then the precleaned gas is raised to thepressure best suited to the following stages by means of a blower,compressor or the like.

The reheating of the raw gas that has been cooled for the separation ofdust and heavy tar is preferably performed in two 'heat exchangers inwhich hotter cleavage gas is circulating, and in a saturator insertedbetween these exchangers. Here the raw gas is further heated,

additionally enriched with water vapor, and heated once again before itis mixed with oxygen and passed over the cleavage catalyst. All thewater streams containing watersoluble tar and gas components are fed tothe saturator at this stage, so that they are totally fed to thecleavage process and thus reduced to the vanishing point as byproducts.

On the catalyst bed of the cleavage reactor, the raw gas, rich in Watervapor and containing oxygen, is decomposed at temperatures between about700 and 1100 C. to a gas consisting mostly of carbon monoxide andhydrogen which also contains lesser quantities of carbon dioxide andwater vapor. Catalysts suitable for the cleavage of the liquid andgaseous hydrocarbons at temperatures above about 700 C. suitably containmetals of the 6th and/or 8th group of the periodic system, or theiroxides or sulfides on a supporting material that is resistant to hightemperatures. Suitable supporting materials are preferentiallyhigh-temperature-resistant oxides of aluminum and/0r magnesium.

Two catalyst layers of components of different activity can be arrangedin the cleavage reactor.

Fundamentally, all catalysts are suitable which, at temperatures aboveabout 700 C., produce an extensive oxidative decomposition of ammonia tonitrogen and Water and a substantially complete oxidative decompositionof hydrocarbons to carbon monoxide and hydrogen.

Special catalysts are, for example, magnesium oxide or aluminum oxidewith 3 to 30% nickel or cobalt or 10% nickel and 10% tungsten, onaluminum oxide and magnesium oxide, said percentages relating to thetotal weight of the catalyst. The catalysts can be sulfurized in aconventional manner.

From the cleavage reactor the gas immediately then enters a waste-"heatboiler for high-pressure steam production, and is here cooled to about550 to 600 C. Further cooling of the cleavage gas is then performed inthe two heat exchangers of the saturation stage placed ahead of thecleavage catalyst. Here the cleavage gas is cooled to about 260 to 300C.

In this cooling process an apparatus can be incorporated which useswater vapor to convert the carbon monoxide contained in the cleavage gasto carbon dioxide and hydrogen, if an especially hydrogen-rich gas is tobe produced.

The gas which is now at a temperature of about 260 to 300 C. is reducedto the temperature required for the gas purification, in for example awaste-heat boiler for the production of low-pressure steam, and inadditional conventional coolers which may be used. The gas purificationitself requires only a simple system for washing out the acid gaseouscompmonents CO and H 8.

The process according to the invention thus solves the problem bycompletely eliminating the recovery of byproducts in the carbonizationand gasification of coals, which has hitherto involved a number ofwastage problems. In the carbonization of coals, especially inmetallurgical coking, coke, gas and water are the end products, while inthe gasification of coals, the ash is the sole solid residue.

This invention will be better understood with reference to theaccompanying drawing in which:

FIG. 1 is a diagrammatic flow chart of a process according to thisinvention wherein coal gasification is accomplished under pressure; and

FIG. 2 is a diagrammatic flow chart of a process ac cording to thisinvention wherein coal gasification is accomplished such that the gascleavage described above is operated on gas at about atmosphericpressure.

In the following examples reference will be made to this drawing fordescriptive purposes. These examples are given by way of illustration ofthis invention and are in no way limiting on the scope hereof.

The installation of FIG. 1 consists substantially of a pressure gasifier1, a washing cooler 2 connected directly thereto with its waste-heatrecovery system 3, heat exchangers 4 and 5 with a saturator 6 insertedbetween them, a cleavage means 7, a high pressure waste-heat boiler 8and a gas scrubber 9.

In the illustrated system, a plant is provided for the conversion of thecarbin monoxide contained in the cleavage gas to hydrogen and carbondioxide by means of water vapor in reactors 10 and 11.

A tar separator 12 for separating the heavy tar from the liquidcirculated through the washing cooler 2 is provided as are an ammoniaseparator 13 with its corresponding condenser 14.

In the pressure gas generator 1, 730 kg. per hour of a coal is gasified,which contains 11.2% moisture, 11.6% ash, 13.1% tar (according toFischer, 4.6% sulfur and 1.2% nitrogen), and has an upper heating valueH =5640 kcal./kg. The coal is fed to the gasifier from the lock hopper15. The gasification agents are 140 m. (STP)/h. of a 90% oxygen and 668kg./h. of high-pressure steam. The oxygen is fed in through a line 16from an air-dissociation plant which is not shown. The high-pressuresteam is taken from a steam accumulator 17 of the highpressurewaste-heat boiler 8, and introduced into the gasifier 1 through line 18.In the gasi'fier, 1000 m. (STP)/h. of raw gas is produced, which passesthrough a connection 19 into the Washing cooler 2 at a pressure of 32atmospheres absolute and a temperature of about 300 C. This raw gas hasthe following gas composition and impurities:

H 3098 kcal./m. (STP).

Accompanying substances:

Tar oil-49.0 g./rn. (STP).

Benzenel4.5 g./m. (STP).

Phenols4.-8 g. m. (STP) Fatty acids0.65 g./m. (STP) Ammonia8 .00 -g./m.('STP) Water vapor content-0.469 kg./-m. (STP).

Organic sulfur compounds-$.63 g./m. (STP), of which 30% COS, 10% CS 25%mercaptan, 30% thiophene.

This gas is cooled in the washing cooler 2 by direct sprinkling withwater, and at the same time is saturated with steam, whereupon theentrained dust and the heavy tar fractions are precipitated andcollected in the sump 20 of the washing cooler.

200 -kg./h. of water together with the dusty tar is taken out of thewashing circuit. To restore the water balance, 197 kg./ h. of water isthen circulated back to the washing cooler 2 through a line 27 by meansof a pump 28. This water is taken mostly from the water separated in thetar remover 12, and some is taken from the condensate from the ammoniaseparation apparatus 13-14. The rest of 50 kg./h. of water is used forinjection into the saturator 6 of the following stage. The tar-dustmixture, consisting of 3 kg./h. of tar and 1 kg./h. of dust, is fed fromthe tar remover 12 through a line 29, by means of a pump 30, back to thegasifier in a prior art manner and mixed with the coal.

By the installation of the waste-heat boiler 3 in the head of thewashing cooler 2, thereby producing kg./h. of low-pressure steam, theemergence temperature of the gas is precisely adjusted to 183 C. and tothe corresponding water-vapor content of 0.466 kg./m. (STP).

The washed raw gas is introduced through a line 31 into the nexttreatment stage, is heated up to 302 C. in the heat exchanger 4, and isfed through a line 32 into the saturator 6. In the latter, the 50 kg./h.of aqueous condensate Which is drawn by a pump 34 through a line 33 fromthe tar remover 12 is vaporized into the hot raw gas, so that, at atemperature of 268 C., the amount of water vapor required for thecleavage, i.e., 0.516 kg./m. (STP), is contained in the gas. Through aline 35 the gas runs into the heat exchanger 5 and is there heated backup to 400 C. The raw gas is heated in heat exchangers 4 and 5 by heatexchange with the cleaved and, if desired, converted gas which flowsfrom the highpressure waste-heat boiler 8 in lines 36, 37, 38 and 40through the conversion reactors 10 and 11 and the heat exchangers 4 and5 into the gas scrubber 9.

The gas flows through a line 41 into the cleavage stage. Here thesuperheated raw gas is mixed with 162 m. (STP)/h. of 90% oxygen from aline 42, and fed into the reactor 7 over the cleavage catalyst,whereupon all higher hydrocarbons and nearly all impurities and most ofthe methane are transformed to carbon monoxide and hydrogen. Thepressure in the cleavage reactor amounts to 30 atmospheres absolute andthe temperature to 900 C. The perceptible heat of this gas from 900 C.down to 400 C. is utilized in the waste-heat boiler 8 attached byflanges to the reactor 7 to provide 877 kg./h. of highpressure steam. Aportion of this steam is fed to the gasiher 1 in the line 18 for thepressure gasification of the solid fuel. The balance of 209 kg./h. isavailable for other purposes, such as gas scrubbing and the like.

The cleavage gas, in a quantity of 1,283 m. (STP)/h., has the followingcomposition and impurities in the line 36 following the waste-heatboiler 8:

Percent CO 24.27 H 8 1.49 25.97 H 42.29 CH; 3.51 N Ar 2.47

H0=2.500 kcal./m. ('STP). 11 0:0453 kg./m. (STP).

In addition to H S and CO as Well as H O the following impurities arestill present:

G. NH 1.0 COS 0.2

The cleavage gas is run through the line 36 at 400 C. into the firstconversion stage 10 from which it passes at 480 C. through a line 37 tothe heat exchanger and is cooled therein down to 380 C. Then it iscarried in a line 38 to the second conversion reactor and furtherconverted therein, a gas output temperature of 400 C. being reached andthe carbon monoxide content being reduced to 5.4%. This gas is carriedin a line 39 to the heat exchanger 4 and cooled in such a manner that itis still available at 290 C. and 29 atmospheres absolute for furtherheat recovery. It is then run into the apparatus designated as the gasscrubber 9 through the line 40, for further cooling, desulfuration andelution of the CO plus additional cooling and drying of the scrubbedgas, if desired. A mixture of CO and H is taken through the line 43.

The converted gas, in a quantity of 1583 m. (STP)/h. has (in line 40)the following composition and nature:

Percent by volume H =2093 kcal./m. (STP). Water vapor content-0.277kg./m. (STP).

8 The following impurities are still present:

G./m. (STP) NH 0.83 COS 0.15

For use as a city gas component, it is sufiicient to remove the H S fromthe gas and part of the CO while the organic sulfur can remain in thegas. The ammonia is absorbed in the condensate when the gas is cooled.This ammoniac condensate is carried in a line 44 from the gas scrubber 9to the ammonia distilling column 13 in which the ammonia is removed bydistillation, so that 390 kg./h. of pure, soft water containing noimpurities leaves the plant through line 45.

When the ammonia is driven out of the water with 22 kg./h. oflow-pressure steam, 47 kg./h. of ammonia concentrate is produced, whichis carried through a line 46 to the condenser 14 where it isprecipitated. The condensate is carried through a line 47 to the tarremover 12, mixed in the latter with other condensates, and fed to thewashing cooler 2 through a line 46 by means of a pump 47 and/or to thesaturator 6 through line 33 by means of a pump 34.

The example described above can be modified by adding oils of foreignorigin to the Washing cooler with the returning condensate, or by addingvolatile hydrocarbons when the water is injected into the saturator 6,these being then cleaved with the gas in the reactor 7, therebyincreasing the yield of gas.

If a mixture of hydrogen and carbon monoxide is to be produced, theconversion reactors 10 and 11 can be omitted. Heat is then supplied tothe heat exchangers 4 and 5 from the hot cleavage gas, in which caselines 36 and 37 on the one hand and lines 38 and 39 on the other handare directly joined and appropriately shortened. The temperature at theoutlet from the waste-heat boiler is then expediently adjusted to about500 C.

The plant shown in FIG. 2 serves for the byproductfree production of agas consisting mainly of hydrogen and carbon monoxide from the volatileproducts of the high-temperature coking of soft coals in so-calledmetallurgical coking.

The plant is connected to the main coming from the roof channels of abattery of horizontal chamber ovens 102. The plant consistssubstantially of a radiation boiler 103, heat exchangers 104 and 105with a saturator 106 between them, a cleavage reactor 107 with awaste-heat boiler 108 directly connected thereto, and a system 109 forcooling and cleaning the cleavage gas.

The raw gas flowing out of the roof channels of the coking oven chambersat about 700 C. passes through the main pipe 101 into the radiationboiler 103 and is here cooled down to about 400 C. At the same time thedust separates. It is fed back to the coking coal, as indicated by theline 111.

By means of a hot gas blower 112, the gas from which the dust has beenremoved is driven from the radiation boiler through line 113 to the heatexchanger 104, where it is heated by indirect heat exchange with the hotcleavage gas from the waste-heat boiler 108 to over 400 C. At thistemperature the gas runs through a line 114 to the saturator 106 inwhich it is enriched with water vapor by the injection of water from aline 115. In line 116 this gas is then heated to over 600 C. by heatexchange with the hot cleavage gas from the Waste-heat boiler 108. Thegas is then fed through a line 117 into the cleavage reactor 107 andmade to react therein on a catalyst bed 118 with oxygen which issupplied through a line 119. A cleavage temperature of over 900 C. ismaintained. The cleavage gas runs from the reactor 107 into theimmediately following waste-heat boiler 108 for preliminary cooling, andis carried from the latter in lines 120 and 121 through the heatexchangers 104 and 105, which are connected in series as regards theheat yielding medium, and through line 122 to the cooling and scrubbingapparatus 109. From this apparatus the pure gas flows at approximatelyambient temperature through line 123, for further utilization.

The steam produced in the steam collector 124 of the radiation boiler103 and in the steam collector 125 of the waste-heat boiler 108 iscombined in line 126 and superheated by a steam superheater 127 by heatexchange with the cleavage gas in line 122, and runs out through line128 for utilization.

In the cooling and scrubbing of the gas in apparatus 109, a watercontaining ammonia is produced. This water is fed through a line 129 toan ammonia still 130 and is bubbled out with steam in the latter. Aclean, soft water is discharged through line 131, which is thenavailable for use as boiler feed water.

The distillate from the ammonia still 130 is condensed in a condenser132 to an ammonia water which is pumped through a line 115 by means of apump 133 to the saturator 106.

The following quantitative example will serve to describe the operationof this system:

1000 m. (STP) of raw coke oven gas in introduced into the system hourlyfrom the coking chamber battery 102. The crude gas has the followingcomposition and H O content-0.362 kg./m. (STP).

Plus the following substances:

G./m. raw gas (STP) Tar oil including naphthaline 100 Benzol 25 Phenols,approx. 1 3 7.5 HCN 2.0 Organic sulfur compounds 0.4

The organic sulfur compounds consist of approximately:

Percent CS Y 50 COS 5 Mercaptans 20 Thiophene 25 This gas, afteremerging from the coking chamber 102 at about 700 C. averagetemperature, is cooled to about 400 C. in the radiation boiler 103 andfreed of dust. This results in the production of 443 kg. of steam at 45atmospheres gauge (line 126). The dust, mixed with fresh coal, is fedback to the coking chamber.

The crude gas at 400 C. is then heated to 537 C. in the heat exchanger104. In saturator 106, 23 kg. of water is vaporized into the hot gas,cooling it to 507 C. In the heat exchanger 105 it is then heated back upto 650 C. It is then mixed in the cleavage reactor 107 with 245 m. (STP)of 95% oxygen and passed over the cleavage catalyst. At the cleavagetemperature of 950 C. which establishes itself, all hydrocarbons andimpurities are to a great extent decomposed and the sulphur compoundsare transformed into hydrogen sulfide and a small percentage of carbonoxysulfide. After the perceptible heat of the cleavage gas has beenutilized in the waste-heat boiler 108, where 374 'kg. of steam at 45atmospheres gauge are produced, it passes at 730 C. into the second heatexchanger and at 613 C. into the first heat exchanger 104. It runs intoline 122 at 500 C. to the steam superheater 127 where is superheats to400 C. the total of 817 kg. of high-pressure steam. At 402 C. and awater vapor content of 0.1595 kg./m. (STP), the cleavage gas inavailable then for recovery of heat, for cooling, and for any furtherpurification, if desired, in apparatus 109, to the extent that may berequired for the purpose for which the gas is desired.

The analysis of the gas is:

Percent CO 4.94 H S 0.25 CO 25.06 H 66.75 CH, 0.15 N 2.85 H 2820kca1./m. (STP).

Impurities G./m. (STP) NH 0.3 COS 0.15

The amount of cleavage gas is 1996 m. (STP).

In the cooling of the gas, approximately 300 kg. of water is producedwhich contains ammonia. In the ammonia still 130, 23 kg. of concentratedammonia is distilled therefrom, and is used for injection into thesaturator 106. The rest of the water is discharged from the plant inpure form.

The high-pressure steam that is produced, which is superheated to 400C., can be used for driving machinery. About half of it suffices tocover the energy requirements of the oxygen plant (air turbocompressor)which supplies the oxygen for the cleavage. The rest can be used invarious other ways.

What is claimed is:

1. In the process for the manufacture of gases comprising substantiallycarbon monoxide and hydrogen by treating tar containing gases producedin the thermal decomposition of solid carbonaceous fuels, wherein thecrude gas evolved in said thermal decomposition of solid carbonaceousfuels is cooled to a temperature of at least about 180 0., therebyfreeing said raw gas from dust and condensible materials produced insaid treatment, the improvement which comprises heating said gas aftersaid cooling with steam to 400 to 550 C., adding oxygen thereto,cleaving said gas-oxygen mixture at a temperature above about 700 C. ona cleaving catalyst thereby converting substantially all hydrocarbonsincluding methane remaining in the gas after said cooling, cooling thecleaved gas to condense steam therefrom and scrubbing said cleaved andcooled gas to remove carbon dioxide, ammonia and sulfur compoundstherefrom.

2. Process as claimed in claim 1, wherein carbon dioxide is added to theraw gas to be cleaved, in addition to the oxygen.

3. A process as claimed in claim 1 including scrub bing the products ofsuch cleavage thereby producing, in addition to said carbonmonoxide-hydrogen gas, a concentrated aqueous ammonia solution;distilling said ammonia solution; and then enriching the raw gasproduced by said treatment with the distillate of said distillation.

4. Process as claimed in claim 1 including enriching said cooled gas andheating such with water vapor obtained by evaporation of the aqueousphase of the condensate separated in the crude gas cooling step and ofsaid concentrated aqueous ammonia solution recovered in the cleaved gasscrubbing step.

5. Process as claimed in claim 1, wherein said thermal decomposition isa carbonization.

6. Process as claimed in claim 1, wherein said thermal decomposition isa gasification of solid carbonaceous 1 1 fuels under elevated pressureand in the presence of oxygen and steam.

7. Process as claimed in claim 1, wherein vaporizable hydrocarbons areadded to the hot raw gas prior to catalytic cleavage.

8. Process as claimed in claim 7, wherein said vaporizable hydrocarbonsare added to said raw gas during said cooling.

9. Process as claimed in claim 1, wherein said cleavage catalystcomprises at least one member selected from the group consisting ofmetals of the 6th and of the 8th group of the periodic system, theiroxides and their sulfides.

10. Process as claimed in claim 9, wherein said catalyst is supported onat least one ceramic material selected from the group consisting ofalumina and magnesia.

1 2 References Cited UNITED STATES PATENTS 3,069,249 12/1962 Herbert etal. 48-497 3,069,250 12/ 1962 Weittenhiller et al. 48-197 3,427,2532/1969 Becker-Boost et al. 23212 X FOREIGN PATENTS 1,159,586 12/1963Germany.

10 JOSEPH SCOVRONEK, Primary Examiner US. Cl. X.R.

